Ignitor

ABSTRACT

A liquid fuel fired ignitor including an atomizing device comprising a tubular barrel and an inner tube projecting into the barrel and discharging into the annular passage formed therebetween and wherein liquid fuel is supplied to the barrel and atomizing fluid is supplied to the tube, with the fuel being atomized by the fluid discharging from the tube and thereafter further atomized by a pair of spaced orifice plates disposed within the barrel downstream fuel flow-wise of the tube.

United States Patent 1191 Sage et a1. Feb. 18, 1975 1 IGNITOR 3,650,4763/1972 Rackley et a]. 239 431 3,747,860 7/1973 Habers 239/431 [75]Inventors: Warnie L. Sage, Louisville; Edwin D. Scott, Alliance, both ofOhio [73] Assignee: The Babcock and Wilcox Company,

New York, NY.

22 Filed: Feb. 27, 1974 21 Appl. No: 446,187

[52] 11.8. Cl 431/354, 239/431, 239/432, 239/434, 431/175 [51] Int. Cl.A62c 31/00, F23d 11/00 [58] Field of Search 239/426, 431, 432, 434;431/167,175, 354

[56] References Cited UNITED STATES PATENTS 1,826,776 10/1931 Gunther..239/434X Primary Examiner-Edward G. Favors Attorney, Agent, orFirm-Joseph M. Maguire; Robert J. Edwards [57] ABSTRACT A liquid fuelfired ignitor including an atomizing device comprising a tubular barreland an inner tube projecting into the barrel and discharging into theannular passage formed therebetween and wherein liquid fuel is suppliedto the barrel and. atomizing fluid is supplied to the tube, with thefuel being atomized by the fluid discharging from the tube andthereafter further atomized by a pair of spaced orifice plates disposedwithin the barrel downstream fuel flow-wise of the tube.

5 Claims, 4 Drawing Figures PATENTEB FEB I 81875 SHEET 2 OF 2 IGNITORBACKGROUND OF THE INVENTION The present invention relates to liquid fueltype ignition systems and more particularly to a device for atomizingthe fuel preparatory to firing from the ignitor.

It is common practice in the design of fuel burning equipment to provideignitors for initiating combustion of the fuel discharged from main fuelburners. Generally, these ignitors are used only intermittently forshort periods, i.e., during start up. and for stabilizing flameconditions during low load and upset conditions. However, on largercentral station vapor generating units, a practice has developed wherebyignitors are used to the exclusion of the main fuel burners to introducethe relatively low fuel input required to heat the vapor generator undercontrolled temperature conditions up to the time when the electricgenerators are synchronized into the main system. This phase of thestart up operation normally takes two to four hours.

Heretofore, liquid fuel type ignitors have resorted to mechanicalatomization of the fuel, a method which, while adequate, has thedisadvantage of giving rise to a highly visible stack plume, anecologically unattractive condition particularly when present over asustained period of time.

SUMMARY OF THE INVENTION The present invention uses a pressurized fluidto atomize the liquid fuel prior to its discharge from the ignitor.

Accordingly, there is provided an ignition system which includes anatomizing device comprising a tubu lar barrel, an inner tube coaxialwith the barrel and projecting thereinto and cooperating therewith toform an annular passage therebetween. A pressurized liquid fuel issupplied to the annular passage and a pressurized atomizing fluid issupplied to the inner tube. The atomizing fluid is at a higher pressurethan the liquid fuel and is discharged into the annular passage througha plurality of ports formed near the distal end of the inner tube andoriented in a direction normal to the barrel and tube axis. The fuelstream flowing through the passage is sheared by the high velocityatomizing fluid exiting from the ports. The fuel leaving the annularpassage is further atomized through impingement and flow velocityincrease as it serially passes through spaced first and second orificesdisposed within the barrel downstream fuel flow-wise of the inner tube.

One embodiment of the invention comprises having the atomizing device asan integral part of the ignitor with the inlet end portion of theignitor nozzle forming the atomizing device tubular barrel. Analternative embodiment includes having the atomizing device as aseparate unit from the ignitor, in which instance, a single device mayprovide atomized fuel to a plurality of ignitors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a sectional side view of themain embodiment of the invention depicting the atomizing device as anintegral part of the ignitor.

FIG. 2 is a side view of an alternate embodiment of the inventionassociated with a main fuel burner and depicting the atomizing device asa unit separate from the ignitor.

FIG. 3 is a schematic plan view of the alternate embodiment of FIG. 2depicting three ignitors serviced by one atomizing device.

FIG. 4 is a sectional side view of the atomizing device as presented inthe alternate embodiment ofFlG. 2 and associated with an ignitor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. I, thereis shown the main embodiment ofthe invention comprising a liquid fuelfired ignitor 10 including a nozzle I2 threadably joined at one end to abody portion l4 and at the other end to a sprayer head 16. The bodyportion 14 contains a passage 18 having an inlet opening 211) to admitliquid fuel to the ignitor I0, and a threaded outlet opening 22, thelatter engages a like threaded segment ofthe inlet portion 24 of thenozzle 12 to provide flow through communication between the passage 18and the bore 26 of nozzle 12. A seal ring 28 is fitted around the inletend 24 adjacent the leading edge of outlet opening 22 to prevent leakageof fuel between the nozzle 12 and the body portion 14.

In accordance with the main embodiment of the invention. the rear endface of the body portion 14 has an opening which admits an internallythreaded tubular coupling 30, the latter being seal-welded to the bodyportion 14. An inner tube 32 projects from within the coupling 30 intothe nozzle inlet end portion 24 which also forms the tubular barrel ofthe atomizing device 34. The tube 32 has an open inlet and a closedoutlet end and discharges through a plurality of ports 36 into anannular passage 33 formed between the cylindrical walls of tubularbarrel 24 and inner tube 32. The ports 36 are circumferentially spacedabout the cylindrical wall near the outlet end of tube 32. The inlet endportion 38 of tube 32 is threaded for engagement with the coupling 30 insuch manner as to permit linear shifting of the position of the ports 36with respect to the inlet and outlet ends of barrel 24 within prescribedlimits. A lock nut 40 fixedly secures the tube 32 to the coupling 30 tomaintain the selected position of the ports 36 with respect to thenozzle 12. It will be appreciated that the allowable range foradjustment of port position is governed by the length of the threadedportion 38. The repositioning of the ports 36 is effected by uncouplingthe nozzle 12 from the body portion 14. loosening the lock nut 40 androtating the tube 32 within the coupling 30 to achieve the desired portlocation with respect to the nozzle 12. When the repositioning of ports36 is complete, the lock nut 40 should be tightened before recouplingthe nozzle 12 to the body portion 14.

The inlet end portion 24 forming the tubular barrel of atomizing device34 includes a pair of spaced orifice plates 42 and 44 situateddownstream fuel flow-wise and in spaced relation to the most forwardposition of the tube 32. Plate 42 is formed with a single orifice 46extending through the center thereof while plate 44 has an imperforatecenter surrounded by a plurality of cir cularly spaced orifices 48. Theoutlet end of nozzle 12 is threaded to receive a like threaded portionof sprayer head I6. The leading end face of the sprayer head I6 isbevelled to form a frusto-conical section for accommodating a pluralityof circularly spaced discharge openings 50 lying in a directiondivergent from the central axis of the nozzle 12.

Referring to FIG. 2, there is shown an alternate embodiment of theinvention in association with a pulverized fuel burner, and including anopening in the furnace wall 52 of a vapor generating unit defined by afrusto-conical burner port 54 having a throat section 56. The innersurface of the port 54 diverges toward the furnace side of the wall 52and is cooled by fluid conducting tubes 58 which line the furnace wall52. Spaced from the wall 52 is a burner windbox front or outer burnerwall 60 which defines therebetween an air chamber or windbox 62 forreceiving a regulated quantity of combustion air. Suitable dampers, notillustrated, may be provided to control the quantity of combustion airdelivered to the windbox 62.

A pulverized fuel burner is partly shown at 64 and includes acylindrical fuel nozzle 66 which extends through an opening in the outerburner wall 60 and across the windbox 62 to a point adjacent the throat56. A distance piece 68 is slidably supported within the fuel nozzle bya suitable spider 70 and is equipped at its distal end with an impeller72, the latter being normally positioned slightly beyond the dischargeend of the fuel nozzle 66. The pulverized fuel is carried from the mill(not shown) in a stream of primary air and is injected into the burnerport 54 by the fuel nozzle 66. Combustion air in the form of secondaryair is supplied to the injected fuel through an air register assembly 74which is disposed within the windbox 62 and adjacent the burner throat56. As shown, theair register assembly 74 is circumferentially spacedabout the discharge end of fuel nozzle 66, and includes front and rearend wall members 76 and 78 and an entrance cone 80 connected to thefurnace wall 52 and converging toward the burner throat 56.Circumferentially spaced and connected between the end wall members 76and 78 and about the periphery thereof are a plurality of air registerdoors 82 which are adapted to pivot between open and closed positions.With the air doors 82 in open position, the air register 74 is renderedin communication with the windbox 62. If desired, the air doors 82 maybe suitably geared, linked or otherwise connected together so as to beresponsive to an operating means (not shown) which may be eithermanually or automatically controlled. In addition to controlling thesecondary air supply, the air register doors 82 are also arranged toimpart a whirling or spinning movement to the air flowing through theregister assembly 74.

An ignitor assembly is depicted at 83 and includes a support tube 86which extends through an opening in the outer burner wall 60 in adirection preferably sloped toward the central axis of the burner port54. The support tube 86 houses a pair of guide tubes 85 and 87 so as toseparately accommodate an electrode 88 and a liquid fuel fired ignitor10A. The electrode 88 is of a type which is well known in the art andcomprises a high voltage lead 90 energized from a suitable high voltagesource such as a transformer (not shown) and connected to one end of anelectrode rod 92, the latter being positioned within the guide tube 85by means of insulators (not shown). Attached to the interior ofguidetube 85 is a ground electrode rod 94 which extends parallel to the rod92 and has formed on its end a right angle bend terminating adjacent theend of rod 94 to form an electric spark gap.

The liquid fuel ignitor 10A extends through the guide tube 87 and hasits sprayer head 16A positioned adjacent the spark gap so that theignitor fuel is readily lighted when the system is energized. The inletend of the guide tube 87 is fitted with a yoke assembly 96 which servesas a coupling seat between the ignitor body portion 14A and liquid fuelconnecting line 98. A leak-proof fit is achieved between the yoke 96 andthe body portion 14A by introducing a gasket (not shown) between themating surfaces and applying pressure with a locking device 99.

in accordance with an alternate embodiment of the invention, theatomizing device 34A is shown as a unit physically separate from theignitor A and comprising a tubular barrel 24A discharging into theliquidfuel connecting line 98. A T-fitting is flow connected to the inlet endof the tubular barrel 24A and includes separate openings communicatingwith an atomizing fluid supply line 27 and a liquid fuel supply line 29.

Referring to FIG. 3 there is shown an arrangement of the alternateembodiment of the invention wherein one atomizing device 34A may besuitably sized to service a plurality of separate ignitor assemblies 83each of which is associated with a different burner port 54 in furnacewall 52.

Referring to FIG. 4 there is shown a detail of the alternativeembodiment of the invention comprising the liquid fuel fired ignitor 10Aincluding a nozzle 12A having one end coupled to a body portion 14A andthe other end fitted with a sprayer head 16A. The nozzle 12A extendsthrough a guide tube 87 and a yoke assembly 96, the latter cooperateswith the ignitor body portion 14A and the locking device 99 to provide atransition means whereby the ignitor 10A may be coupled and uncoupledfrom the liquid fuel connecting line 98. The yoke assembly 96 includes apassage 17 which cooperates with the passage 18A and the bore 26A topermit uninterrupted fuel flow through the ignitor 10A. The liquid fuelconnecting line 98 has its outlet end connected to the yoke assembly 96at passage 17 and its inlet end connected to the outlet end of tubularbarrel 24A. The T-fitting 25 has one end connected to the inlet end ofbarrel 24A, its second end connected to the liquid fuel supply line 29and its third end connected to a plug member 23, the aforementionedconnections are preferably threaded in order to facilitate dismantlingof the ignitor system for cleaning and maintenance.

The plug member 23 has an opening which admits an internally threadedtubular coupling A, the latter is connected at its inlet end to theatomizing fluid supply line 27. An inner tube 32A projects from withinthe coupling 30A into the tubular barrel 24A. The tube 32A has a closedoutlet end and an open inlet end 38A, the, latter being threadablyengaged with the outlet end of coupling 30A. The inner tube 32Adischarges through a plurality of ports 36A into an annular passage 33Aformed between the cylindrical walls of tubular barrel 24A and innertube 32A. The ports 36A are circumferentially spaced about thecylindrical wall near the outlet end of tube 32A. The length ofthreading of the inlet end 38A provides a range of adjustment wherebythe position of the ports 36A may be linearly shifted with respect tothe inlet and outlet ends of the tubular barrel 24A. A lock nut Afixedly secures the tube 32A to maintain the selected position of theports 36A with respect to the barrel 24A. The repositioning of the ports36A is effected by uncoupling the plug member 23 from the T-fitting 25and removing therewith the coupling 30A and associated tube 32A,thereafter, loosening the lock nut 40A and rotating the tube 32A withinthe coupling 30A to achieve the desired port location with respect tothe tubular barrel 24A. When the repositioning of ports 36A is complete,the lock nut 40A should be tightened before recoupling the plug member23 to the T-fitting 25.

During operation of the main embodiment of the invention, pressurizedliquid, e.g., fuel oil, is admitted to the ignitor at opening and flowsthrough passage 18 into the annular passage 33 where it is atomized bypressurized fluid, e.g., air, exiting from the inner tube 32 through thedischarge ports 36. The liquid fuel is thereafter further atomized as itis serially conveyed through the orifice plates 42 and 44, theatomization resulting from impingement on the imperforate portions ofplates 42 and 44, and the velocity increases experienced during passagethrough the orifice openings 46 and 48. A final stage of atomizationoccurs as the liquid fuel discharges through the openings 50 of sprayerhead 16.

In the operation of the alternate embodiment of the invention, thesupply line 29 delivers pressurized liquid, e.g., fuel oil, to theT-fitting for flow into the annular passage 33A. The supply line 27delivers pressurized atomizing fluid, e.g., air, into the inner tube32A. The liquid fuel flowing through passage 33A is atomized by thefluid discharging from ports 36A. The liquid fuel is thereafter furtheratomized as it is serially conveyed through the orifice plates 42A and44A, the atomization resulting from impingement on the imperforateportions of plates 42A and 44A, and the velocity increases experiencedduring passage through the orifice openings 46A and 48A. The liquid fuelleaving the atom izing device 34A passes through a coupling 97 and aconnecting line 98 for delivery to the ignitor 10A wherein there occursa final stage of atomization as the fuel discharges through the openings50A of sprayer head 16A.

In the operation of the atomizing device of the present invention, theatomizing fluid pressure at the inlet to the device will be at a highervalue than that of the liquid fuel entering the device. The differencein pressure varies in accordance with the type of atomizing fluid and/orthe type of liquid fuel to be atomized.

While in accordance with provisions of the statutes there is illustratedand described herein a specific embodiment of the invention, thoseskilled in the art will understand that changes may be made in the formof the invention covered by the claims, and that certain features of theinvention may sometimes be used to advantage without a corresponding useof the other features.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A liquid fuel fired ignition system comprising at least one ignitor.a device for atomizing the fuel preparatory to firing from the ignitor.said device including a nozzle having an inlet and an outlet end, acoupling connected to the inlet end, an inner tube disposed in saidcoupling and projectingv into the nozzle through the inlet end thereof,said tube cooperating with the nozzle to define therebetween an annularpassage of uniform dimension throughout, said tube having an outletformed of at least one port opening into the passage and an inlet formedwith a threaded portion, a sleeve mounted in the coupling, said sleevehaving a threaded portion engaging the threaded portion of the tubewhile permitting rotatable and axial adjustment of said tube, means forsupplying a liquid fuel to the passage and an atomizing fluid to thetube, the fuel being atomized by the fluid discharging from said port,and a pair of spaced perforated dislks disposed within the nozzledownstream fuel flow-wise of said tube, the fuel being further atomizedwhile passing through said disks.

2. The system according to claim 1 wherein the atomizing device is anintegral part of the ignitor.

3. The system according to claim 1 wherein the atomizing device isseparate from the ignitor, and including conduit means flow connectingthe device to said ignitor.

4. The system according to claim 1 comprising a plurality of ignitors,said atomizing device being separate from the ignitors, and includingconduit means flow connecting the device to said ig'nitors.

5. The system according to'claim 1 including a lock nut engaging thethreaded portion of said tube to fixedly secure the tube to said sleevethereby maintaining the tube in the selected position.

* l l -l l=

1. A liquid fuel fired ignition system comprising at least one ignitor, a device for atomizing the fuel preparatory to firing from the ignitor, said device including a nozzle having an inlet and an outlet end, a coupling connected to the inlet end, an inner tube disposed in said coupling and projecting into the nozzle through the inlet end thereof, said tube cooperating with the nozzle to define therebetween an annular passage of uniform dimension throughout, said tube having an outlet formed of at least one port opening into the passage and an inlet formed with a threaded portion, a sleeve mounted in the coupling, said sleeve having a threaded portion engaging the threaded portion of the tube while permitting rotatable and axial adjustment of said tube, means for supplying a liquid fuel to the passage and an atomizing fluid to the tube, the fuel being atomized by the fluid discharging from said port, and a pair of spaced perforated disks disposed within the nozzle downstream fuel flow-wise of said tube, the fuel being further atomized while passing through said disks.
 2. The system according to claim 1 wherein the atomizing device is an integral part of the ignitor.
 3. The system according to claim 1 wherein the atomizing device is separate from the ignitor, and including conduit means flow connecting the device to said ignitor.
 4. The system according to claim 1 comprising a plurality of ignitors, said atomizing device being separate from the ignitors, and including conduit means flow connecting the device to said ignitors.
 5. The system according to claim 1 including a lock nut engaging the threaded portion of said tube to fixedly secure the tube to said sleeve thereby maintaining the tube in the selected position. 